1. Field of the Invention
This invention relates to the brazing art and more particularly, to high strength and corrosion-resistant aluminum alloys for brazing which exhibit high strength after brazing and are excellent in corrosion resistance.
2. Description of the Prior Art
Brazing of aluminium or aluminium alloys thereof has been widely effected mainly on heat exchanges of automobiles. For instance, aluminium materials of 1000 and 3000 series are now applied to condensers and evaporators for car air conditioners and to oil coolers for engines.
In recent years, furthermore, use of aluminium alloys in automobile radiator is increasing. Because high strength is needed for automobile radiator material, Al-Mn-Mg alloys of 3000 series or alloys of 6000 series are currently used.
Especially, 6000 series alloys are heat treatable aluminium alloys, of which 6951 alloy, which is a high strength alloy for brazing is standardized as a core material for brazing sheet in the JIS and AA standards and is mainly applied as a header material for automobile radiator.
However, this 6951 alloy is apt to be attacked by filler metal at brazing. Although the alloy is slightly better in corrosion resistance than other alloys having almost the same level of strength, its resistance to corrosion is much lower than as required.
Moreover, in heat exchangers for use in automobiles, there is a strong demand of rendering a material as thin as possible in order to make light and compact heat exchangers. This, in turn, highly requires an aluminium alloy which is high in strength and excellent in corrosion resistance.